But a good portion of today's free agents aren't working that way voluntarily. They would prefer the steadier situation of regular employment. They may have been laid off during the downturn, or they may be straight out of college and eager to grasp the lowest rung of the career ladder.

For these folks, temp or contractor work is a last resort rather than a first choice. They are more un-free than free agents. As such, they probably enter into work assignments with an engagement deficit. They may be determined to do a decent job, but by definition aren't thrilled to be working as they are.

It's hard to say what percentage of contingents are the un-free ones. The U.S. Department of Labor hasn't studied the topic since 2005. At that point, more than half of contingent workers--55 percent--would have preferred a permanent job.

For a mini-portrait of an involuntary contingent worker today, consider Laurie Barnes. Laid off by consulting firm Mercer in 2010, theChicagoresident is the midst of a nine-month contract through a staffing agency. She is grateful for her project, which involves revamping a talent management program for a company, and expects to be able to tout it as she pursues future opportunities. But she misses traditional employment. For one thing, she would like the financial stability—including retirement and health care benefits—of a full-time job.

She also wants to get back on the corporate career ladder. "I'm later in my career but by no means am I ready to plateau," says, Barnes, who has spent 20 years in the field of HR consulting. "As a contractor, it's a plateau."

To Barnes and others, the very language around impermanent work can sting. "The word 'contractor' connotes 'task,' 'a pair of hands,' 'fill-in,' " Barnes says. "It doesn't necessarily convey 'strategy,' 'someone who moves us forward.' It's just a warm body."

If companies want to get the most of their "warm bodies," they need to see things from the perspective of un-free agents. If they do, firms are more likely to take some simple steps to improve matters for both sides. Steps like working hard to treat temps as people rather than cogs in day-to-day office encounters. Like including contingents in social events and offering feedback. Like soliciting contingents' ideas about strategic matters and inviting them to apply for full-time openings. In short, companies are more likely to give contingents an "arms-length embrace."

And that is likely to encourage impermanent workers to care a bit more, to work a bit harder, to produce better results.